The calculated distance (air line) between Daejeon and Yangp'yŏng is approximately 79 miles respectively 127 kilometers.
By car or train, the actual journey to Yangp'yŏng is certainly longer, as only the direct route (as the crow flies) between Daejeon and Yangp'yŏng has been calculated here.
Air line (approximately)
127 kilometers
69 nautical miles